The present invention relates to the field of electrical conductor cables. More specifically, the present invention relates to vibration dampers for limiting wind-induced vibration of the conductor cables.
Electrical conductor cables suspended overhead from poles and/or towers are subject to a wind induced vibration identified as aeolian vibration. A typical overhead conductor for high voltage transmission of electrical power is comprised of a multi-strand conductor. Even though the amplitude or intensity of aeolian vibration is small (rarely more than the diameter of the conductor when measured from peak to peak), the effect of such a vibration is to cause the conductor strands and/or conductor supports to fail in fatigue.
One method of combating wind induced vibration is by the use of damping devices, one being the well-known Stockbridge damper. The Stockbridge damper includes a symmetrical arrangement of weights and messenger cable clamped to the electrical conductor. The function of the Stockbridge damper is to transform the vibratory motion of the conductor into another form of energy, namely, heat from friction between the strands of the messenger cable, and dissipate this heat to the atmosphere.
Vibration dampers are typically installed on electrical conductors during new construction when the electrical conductors are not yet energized. During new construction, a vibration damper can be easily installed on a conductor by hand by mounting a conductor clamp of the vibration damper onto the conductor. A capscrew on the conductor clamp is then tightened using a hand-held wrench or socket wrench to secure the vibration damper onto the conductor.
Occasionally, it is desirable to add vibration dampers on existing construction in which the electrical conductors are already energized. For example, in areas where conductor and/or support hardware failures have occurred due to wind-induced vibration, corrective action may be required to prevent additional component failures. The method of installation of vibration dampers utilized during new construction often cannot be employed on existing construction without taking a planned power outage. That is, the energized conductors must be de-energized before a lineman can install the vibration dampers onto the existing electrical conductors.
Obviously, de-energizing conductors even for a short duration is an unsatisfactory situation. Power outages, planned or otherwise, are inconvenient, disrupting the operation of electrically-powered heating and air conditioning systems, mass transportation systems, appliances, computing systems, and so forth. Moreover, a power outage that disrupts the operation of traffic signals, hospital equipment, and so forth can endanger lives. Accordingly, it is highly desirable that electrical conductors remain energized when installing vibration dampers on existing construction.
Working on energized electrical conductors, such as high voltage power lines, is hazardous. Service personnel for power companies typically utilize apparatuses referred to as live line tools, such as, hot sticks, shotgun sticks, gripall sticks, or clamp sticks, when working on electrical conductors or for manipulating various other tools that contact the electrical conductors. A hot stick provides electrical insulation for a lineman and allows a lineman to maintain a safe working clearance from the energized conductor.
FIG. 1 shows a perspective view of a prior art Stockbridge-type vibration damper 20. Damper 20 includes weights 22, a messenger cable 24, and a clamp 26. Clamp 26 includes a base 28 having a cable housing 30 for attachment to messenger cable 24 and a first clamp member 32. Clamp 26 further includes a second clamp member 34. A capscrew 36 secures second clamp member 34 to first clamp member 32.
A common method used to install vibration damper 20 on an energized conductor involves utilization of a first hot stick by a first lineman to hold vibration damper 20 by messenger cable 24 and position it on the conductor, maintaining a downward force on the first hot stick. To facilitate installation, capscrew 36 must be retracted far enough to allow the conductor to fit between first clamp member 32 and second clamp member 34. Unfortunately, if second clamp member 34 is bumped slightly, second clamp member 34 can rotate about capscrew 36 as represented by an arrow 38. Consequently, once clamp 26 is positioned on the energized conductor, a second lineman using a second hot stick with a socket on the end captures capscrew 36 and alternately tightens capscrew 36 and moves second clamp member 34 back to its original position, potentially requiring the use of a third hot stick.
Accordingly, installation of the vibration dampers on energized conductors requires two lineman manipulating two or more hot sticks, and potentially two pieces of equipment, typically referred to as cherry pickers, each having a maneuverable vertical boom with an open bucket at the end from which the lineman can perform the installation. Bucket repositioning may or may not be required during the installation to ensure that adequate leverage can be maintained to perform the tasks while maintaining appropriate clearances between the linemen and the energized conductor.
A typical vibration damper weighs approximately six to twelve pounds. When a lineman is working on a suspended conductor, the conductor may be as much as twelve feet from the lineman. Thus, a lineman may utilize a hot stick of approximately twelve feet in length in order to reach the conductor. Experience has shown that the installation of a vibration damper on an energized conductor takes two experienced linemen approximately ten to fifteen minutes per damper installation. The weight of the vibration damper, supported on an end of the hot stick remote from the lineman, is unwieldy, thus requiring significant strength to support the vibration damper for such a duration.
Moreover, the duration combined with the use of two linemen for each installation significantly drives up the cost of each installation. Thus, what is needed is mechanism and method for rapidly installing a vibration damper utilizing a single lineman.
Accordingly, it is an advantage of the present invention that a clamp for a vibration damper and a method for installing the vibration damper is provided.
Another advantage of the present invention is that a clamp is provided that is resistant to rotation during installation.
It is another advantage of the present invention that a clamp for a vibration damper is provided that enables a single lineman to install the vibration damper.
Yet another advantage of the present invention is that the clamp enables the vibration damper to be rapidly installed on an energized conductor using a single live line tool.
The above and other advantages of the present invention are carried out in one form in a vibration damper by a clamp for attachment to a suspended conductor, the vibration damper including a damping structure. The clamp includes a base having a housing for attachment to the damping structure and a first clamp member extending from the housing. The first clamp member has a first extension section and a second extension section. A second clamp member is positioned between the first and second extension sections. The first and second clamp members cooperate to provide a passageway for the suspended conductor. A fastener secures the second clamp member to the first clamp member, and the first and second extension sections continuously abut the second clamp member to prevent rotation of the second clamp member about the fastener.
The above and other advantages of the present invention are carried out in another form by a method for installing a vibration damper on an energized suspended cable using a shotgun stick. The vibration damper includes a clamp for attachment to the suspended conductor, the clamp including a first clamp member, a second clamp member, and an eyebolt for securing the second clamp member to the first clamp member. The method calls for directing the eyebolt through the second clamp member and into a receiving portion of the first clamp member to secure the second clamp member to the first clamp member in a loosened configuration. The method further calls for capturing a loop portion of the eyebolt by a hook member slidably mounted within a head of the shotgun stick. The vibration damper is manipulated by the loop portion of the eyebolt using the shotgun stick. The manipulating operation enables passage of the energized suspended conductor in a passageway formed between the first and second clamp members. The shotgun stick is rotated to impart rotational motion on the eyebolt to engage a threaded portion of the eyebolt with the receiving portion of the first clamp member to retain the clamp on the energized suspended conductor. The loop portion of the eyebolt is then released from the hook member.